Diazo print process



United States Patent Ofiiice 3,348,947 Patented Oct. 24:, 1967 3,348,947 DIAZO PRINT PROtIESS Charles A. Girard, Lexington, and Francis R. Clarke, Nicholasville, Ky., assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York No Drawing. Filed Dec. 18. 1953, Ser. No. 331,356 23 Claims. (Cl. 96-49) This invention relates to the production of prints from light sensitive diazo materials. More particularly, this invention relates to a new and useful base generating process to develop diazotype papers of the type spoken of in the art as two-component diazotypes (Ozalid-type). It also relates to new materials to be utilized in the abovementioned process and which are more eliicacious than their known counterparts.

The use of organic compounds as light-sensitive media for photographic purposes is well known, and is perhaps best exemplified by the diazo process. This process is based on'the phototchemical changes effected in various diazonium salts upon exposure to light, and which alfect their capacity to form dyes. In general, dyes are formed with the diazonium compounds, or diazotized amines, couple with phenols or aromatic amines in an alkaline medium. Upon exposure to light, the diazonium compounds undergo decomposition and are rendered incapable of coupling and, therefore, incapable of forming the corresponding dyestuffs through the coupling process. After light exposure and development, a dyestuff is formed at the portions of the light sensitive material which have not been exposed to light (i.e., at portions on the light sensitive material which have been protected by the pattern or design on the material to be copied) and thus a positive record is obtained from a positive image.

While copying papers of this type have been successfully used for years, they are subject to the drawback that an external application of a developing fluid (either liquid or gaseous) is required whereby the alkaline condition needed for dye formation is produced.

In the wet development process, it has been the practice to employ an alkaline, buffered aqueous solution containing a coupler that is applied to the diazotype paper after light exposure. This results in the azo-dye formation at the areas of the light sensitive material which have not been light exposed. This method, however, has the following disadvantages:

(l) The coupler in the alkaline aqueous solution is easily oxidized because of the basicity of the solution. This produces a developing solution which discolors the diazo paper during development thereof.

(2) There is a leaching of the azo-dye from the copying paper because of the extensive solubility of the azodyes in the basic aqueous solutions.

(3) The coupling solutions utilized in the wet development systems are saturated with the necessary ingredients. Use thereof results in the precipitation of various solids from the solution because of the decrease in the ambient temperature and/or the evaporation of the solvent (i.e. water).

(4) The developing solutions usually contain a mixture of ingredients which are selectively absorbed by the copying paper during the development process. This results in non-uniform color reproduction as the solution is used during a given period.

In the dry development process, it has been the practice to utilize gaseous moist ammonia applied to the light exposed diazotype paper as the developing agent. In various instances, a second sheet (i.e., the developer sheet) is impregnated with an alkaline generating material which when heated will yield ammonia by decomposition. In other words, this method contemplates the utilization of merely two sheets of paper-one containing the latent image in the form of unreacted diazo and diazo coupling components and the other containing a compound which under proper conditions releases an alkalyzing medium in direct contact with the imaged surface to develop the latent image by promoting the coupling reaction through the adjustment of the ambient pH conditions.

More specific references relating to this method of development can be seen in the following US. patents: 1,966,755, 2,228,562, 2,774,669, and 3,046,128.

In US. Patent No. 1,966,755 it was proposed that an aromatic amine impregnated sheet be utilized as the developing agent. This method, however, has the following disadvantages:

(l) The aromatic amines are easily oxidized and will also evaporate slowly from the paper upon standing; this results in a lack of uniformity in reproductions and, in general, poor quality reproductions if the aromatic amine impregnated developer paper has been standing for a lengthy period of time before use.

(2) Aromatic amines have a measurable vapor pressure even at room temperature so that the storage life of such a sheet is limited.

(3) Aromatic amines are very weak bases and do not supply a good alkaline environment in which the dye formation can occur.

(4) Additionally, the aromatic amines are highly toxic and have a pronounced and undesirable odor. In US. Patents Nos. 2,228,562, 2,774,699, and 3,046,128 there is proposed the utilization of a developer sheet containing a compound, or compounds, which, upon heating, will yield gaseous ammonia. The vapor so produced will contact the light exposed diazotype paper, raise the pH of the sensitized layer and thereby promote the coupling reaction between the unexposed diazo compound and the cou pling component which results in the formation of the colored image. Various ammonia generating substances which have been shown to be applicable are ammonium carbonate; ammonium salts of weak acids, such as ammonium acetate, ammonium formate, and ammonium oleate; urea and alkyl substituted ureas; and chromium hexamino compounds. These methods suffer from numerous disadvantages some of which are noted as follows:

(1) The processes involving the production of ammonia gas as the alkalyzing medium require a large amount of the ammonia forming compound because of the high volatility of ammonia and the resulting poor entrapment of the vapor on the diazotype paper.

(2) The ammonia fumes so produced have an obnoxious odor which, of course, renders the immediate working areas unpleasant to the operating personnel. Additionally, the ammonia vapors are highly corrosive to the machinery involved.

(3) The necessity of providing a water former for processes that utilize ammonia gas.

(4) The use of hydrolysis of ammonium carbonate or other ammonium salts of weak acids by atmospheric water resulting in a gradual loss of the base generator from the developer paper. This, of course, results in a reduction of efiicacy when the developer paper is subsequently utilized.

(5) The escape of ammonia vapors from the duplicating apparatus may promote premature color formation among stored diazotype copying sheets which may be in the adjacent areas.

It is, therefore, the object of the present invention to overcome the disadvantages of diazotype development processes and to permit development by simple and rapid steps without the necessity for complex equipment or the production of obnoxious atmospheres.

It is the object of the present invention to describe a new and useful base generating process whereby the dematerials which have good development characteristicsv and which have good storage characteristics.

Another object is to provide a stable aqueous developer solution which is not subject to the various disadvantages which permeate the prior materials utilized for similar purposes.

Another object is to provide an improved dry diazotype developer sheet which has impregnated thereon a stable chemical agent or composition which, upon the application of heat, will produce alkaline vapors capable of promoting the diazo coupling reaction.

Another object is to provide dry diazotype developer materials which are caused to release alkaline vapors solely by the application of heat.

A further object is to provide dry diazotype developer materials which have good storage characteristics.

These and other objects and advantages of the present invention will be apparent from the following discussion, and as such are intended to be objects thereof, whether enumerated or not.

These and other objects are accomplished by the process of the present invention which comprises exposing a two-component diazotype paper under a pattern to a suitable light source, contacting the exposed sheet with an amine oxide and thereafter heating to 250 to 400 F. The application of heat transforms the amine oxides into strong alkaline materials which promote the coupling reaction so as to form an image. In particular, the application of heat results in the thermal decomposition of the amine oxides with the resultant formation of aromatic or aliphatic hydroxyl amines; or amines, water and olefins, Since amines, and hydroxyl amines are strong bases the diazo compound undergoes coupling with the coupler present in the two-component diazotype paper so as to form the visual azo-dye in the image areas.

Preferred amine oxide compounds which, under application of heat, decompose to form strong alkaline materials, and which are applicable to processes for the alkaline development of diazotype papers are trimethyl amine oxide, triethyl amine oxide, tributyl amine oxide, and N-methyl-morpholine oxide.

In general, the use of amine oxides as the base generating compounds have distinct advantages over all previously disclosed base-generators. Amine oxides are similar to inorganic salts in that they are non-volatile; additionally, such compounds are stable in liquid solutions and exert no measurable vapor pressure. Amine oxides are generally coordinated with at least one mole of water which will provide the necessary water for the azo-dye formation. Further, aqueous solutions of amine oxides .do not evaporate to dryness because of the hygroscopic nature of the amine oxides. Even when coated on paper and dried the amine oxides, since they are hydrated, re-

tain sufficient moisture to produce an ideal environment pling with a coupler in the two-component system to form an azo dye in the image areas.

A typical system for accomplishing theabove objectives consists of coating paper with an aqueous solution of p-diazo-2,5-diethoxy N morpholinoaniline chloride, half-zinc chloride salt; 6,7-dihydroxy-2-naphthalene sodium sulfonate and citric acid. After drying, the paper is exposed under a positive master to ultraviolet light. The light-exposed paper is treated with an aqueous amine oxide solution, and thereafter dried at 350 F. whereupon a usable image is formed in the unexposed areas. Although amine oxides, in general, are applicable to this wet development process, the preferred amine oxide is N- methyl-morpholine oxide.

The prepared diazotype paper has, preferably, a range of 20 to 150 grams per 1000 square feet of the p-diazo- 2,S-diethoxy-N-morpholinoaniline chloride, half-zinc chloride salt. The 6,7-dihydroxy-2-naphthalene sodium sul fonate is in a range of 10 to 75 grams per 1000 square feet of paper and the citric acid is in a range of 20 to grams per 1000 square feet of paper.

In utilizing the wet development process the concentration of the aqueous amine oxide solution has a'substantial range. However, for the following examples of amine oxides the range of concentration is set forth as being illustrative of the precepts of the invention:

Percent Trimethyl amine oxide 1-30 Triethyl amine oxide 1-30 Tributyl amine oxide 1-30 N-methyl-morpholine oxide 1-30 The present invention is also applicable to the socalled dry development process wherein a second sheet which has impregnated therein an alkaline generating material is placed into contiguous relationship with a light exposed two-component diazotype paper. The application of heat to the materials while in the contiguous relationship promotes. the formation of the alkaline material whereupon the ambient pH conditions are sufficiently changed to effectuate the coupling reaction with the resultant formation of the visual image.

In particular, it is possible to form a usable image from a previously light exposed two-component diazotype paper by placing a second sheet of paper that has been coated with an amine oxide on top of the diazotype paper and applying heat at 350-400 F.

In utilizing the dry development process the quantity applicable of the amine oxide deposited on the second sheet has a substantial range. However, for the following examples of amine oxides the number of grams utilized per area of 1000 square feet of second sheet is recommended:

Grams Trimethyl amine oxide 100 Triethyl amine oxide 12.0 Tributyl amine oxide 200 N-methyl-morpholine oxide Atypical system for accomplishing the above objectives consists of coating paper with an aqueous solution of triethylamine oxide and allowing the paper to dry. This base generating paper can then be used to develop light exposed two-component diazotype paper that has been coated with, for example, p-diazo-N-ethyLN-benzyl-' aniline zinc chloride-half-zinc chloride salt; 6,7-dihydroxy-2-naphthalene sodium sulfonate and glycolic acid. The method of development consists of placing the amine oxide coated paper against the diazotype paper, both coatings being in intimate contact, and subsequently heating the so-contacted papers at 350400 F. for l to 5 seconds between two heated metal plates.

The'prepared diazotype paper has, preferably, a range of 20 to grams per 1000 square feet of the p-diazo- N ethyl-N-benzylaniline zinc chloride-half-zinc chloride salt. The 6,7-dihydroxy-Z-naphthalene sodium sulfonate is in a range of to 75 grams per 1000 square feet of paper and the glycolic acid is in a range of 20 to 80 grams per 1000 square feet of paper.

It should be noted that the diazo compound, the coupling component, and adjuncts are not critical factors in the practice of the present invention. Additionally, the incorporation of background stabilizers, humectants, diazostabilizers, binders, etc., to the diazotype paper, film, etc., are advantageous, but not in any way necessary for the accomplishment of the objectives of the present invention.

While the invention has been particularly described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A process for the development of a visual image by the chemical reaction of a light-sensitive diazonium compound and an azo dye coupler, in an alkaline medium, comprising exposing a material sensitized with a twocomponent diazonium coating to light under a positive, contacting said light-exposed two-component diazotype material with an amine oxide, and thereafter heating said material to produce alkaline vapors whereby an image develops on the unexposed areas of said light-exposed two-component diazotype material.

2. The process of claim 1 wherein the material is heated to 250400- F.

3. The process of claim 1 wherein the materal is heated to 250-400 F. for 1-5 seconds.

4. The process of claim 1 wherein the amine oxide is trimethyl amine oxide.

5. The process of claim 1 wherein the amine oxide is tributyl amine oxide.

6. The process of claim 1 wherein the amine oxide is triethyl amine oxide.

7. The process of claim 1 wherein the amine oxide is N-methyl-morpholine oxide.

8. A process for the wet development of a visual image by the chemical reaction of a light-sensitive diazonium compound and an azo dye coupler, in an alkaline medium, comprising exposing a material sensitized with a twocomponent diazonium coating to light under a positive,

coating said light-exposed two-component diazotype material with an aqueous amine oxide solution, and thereafter heating said material to produce alkaline vapors whereby an image develops on the unexposed areas of said light-exposed two-component diazotype material.

9. The process of claim 8 wherein the material is heated to 250-400 F.

10. The process of claim 8 wherein the amine oxide is trimethyl amine oxide.

11. The process of claim 8 wherein the amine oxide is tributyl amine oxide.

12. The process of claim 8 wherein the amine oxide is triethyl amine oxide.

13. The process of claim 8 wherein the amine oxide is N-methyl-morpholine oxide.

14. A process for the dry development of a visual image by the chemical reaction of a light-sensitive diazonium compound and an azo-dye coupler, in an alkaline medium, comprising exposing a material sensitized with a two-component diazonium coating to light under a positive, contacting said light-exposed two-component diazotype material with a dry support having coated thereon an amine oxide, and thereafter heating said materials while in continguous relationship whereby an image develops on the unexposed areas of said light-exposed two-component diazotype material.

15. The process of claim 14 wherein the material is heated to 250400 F.

16. The process of claim 14 wherein the material is heated to 250-400 F. for 1-5 seconds.

17. The process of claim 14 wherein the amine oxide is trimethyl amine oxide.

18. The process of claim 14 wherein the amine oxide is tributyl amine oxide.

19. The process of claim 14 wherein the amine oxide is triethyl amine oxide.

20. The process of claim 14 wherein the amine oxide is N-methyl-morpholine oxide.

21. A process for the development of a visual image by the chemical reaction of a light-sensitive diazonium compound and an azo-dye coupler, in an alkaline medium, comprising exposing a material sensitized with a twocomponent diazonium coating to light under a positive, contacting said light-exposed two-component diazotype material with an amine oxide, and thereafter heating said material to decompose said amine oxide so as to produce alkaline vapors whereby an image develops on the unexposed areas of said light-exposed two-components diazotype material.

22. A process for the development of .a visual image by the chemical reaction of a light-sensitive diazonium compound and an azo-dye coupler, in an alkaline medium, comprising of exposing a material sensitized with a twocomponent diazonium coating to light under a positive, contacting said light-exposed two-component diazotype material with an amine oxide, and thereafter heating said material so as to subject said light-exposed two-component diazotype material to the thermal decomposition products of said amine oxide.

23. The process of claim 8 wherein the material is heated to 250-400 F. for 1-5 seconds.

References Cited UNITED STATES PATENTS 2,169,976 8/1939 Guenther et a1. 885 2,308,058 1/1943 Crowley et a1. 96--49 2,367,273 1/1945 Hall et .al. 8-128 2,687,442 8/ 1954 Claver 260-650 XR 2,769,824 11/1956 Schneider et al.

260-483 D XR 3,047,579 7/1962 Witman 260-583 D 3,060,023 10/1962 Burg et al 96115 P XR 3,135,607 6/1964 Hills 9691 XR OTHER REFERENCES Heibron, Sir Ian, Dictionary of Organic Compounds, vol. IV, Oxford Univ. Press, N.Y., 1953, QD25 1H45 1953 C. 4, (pp. 591592 relied on).

NORMAN G. TORCHIN, Primary Examiner.

C. L. BOWERS, J R., Assistant Examiner. 

1. A PROCESS FOR THE DEVELOPMENT OF A VISUAL IMAGE BY THE CHEMICAL REACTION OF A LIGHT-SENSITIVE DIAZONIUM COMPOUND AND AN AZO DYE COUPLER, IN AN ALKALINE MEDIUM, COMPRISING EXPOSING A MATERIAL SENSITIZED WITH A TWOCOMPONENT DIAZONIUM COATING TO LIGHT UNDER A POSITIVE, CONTACTING SAID LIGHT-EXPOSED TWO-COMPONENT DIAZOTYPE MATERIAL WITH AN AMINE OXIDE, AND THEREAFTER HEATING SAID MATERIAL TO PRODUCE ALKALINE VAPORS WHEREBY AN IMAGE DEVELOPS ON THE UNEXPOSED AREAS OF SAID LIGHT-EXPOSED TWO-COMPONENT DIAZOTYPE MATERIAL. 